One of the many methods known for leak testing a wall, or more particularly for testing the porosity of any part, is a method which consists essentially in forming a sealed enclosure using said part to be tested and in applying a gas up to a given pressure to said enclosure and then observing variations in the pressure of the gas therein relative to the pressure at which it stabilizes. Obviously the materials used, other than those of the part under test, are specially chosen so as not to be porous, are the gaskets which provide sealing between the various materials making up the enclosure.
In most cases pressure falls off fairly slowly. The rate at which the pressure falls off is representative of the porosity of the wall of the part under test. A part is generally considered good when the rate at which the pressure falls off does not exceed a given threshold, as predetermined by technicians skilled in the art.
The known method outlined above gives good test results and enables good parts to be distinguished from bad parts.
FIG. 1 is a diagrammatic graph showing variation of gas pressure inside the enclosure as a function of elapsed time plotted in arbitrary units. Thus, it can be seen that between instants t.sub.0 and t.sub.1 the pressure increases rapidly inside the enclosure due to the enclosure being directly connected to a source of compressed gas. Once the pressure has reached a maximum value, the supply is turned off. Random pressure variations then take place between instants t.sub.1 and t.sub.2. The duration of such phenomena constitute what technicians call "the stabilization time" during which no meaningful measurements can be taken. In known methods using compressed air, the stabilization time may be as much as 25 seconds. Although this period of time is not very great in itself, when compared with the time taken to fabricate the part in question and with the quantity of parts produced, this time becomes too large and is a factor which limits production. Given that the time required for the pressure rise from t.sub.0 to t.sub.1, and the time required to perform measurements .DELTA.p.sub.43 and .DELTA.p.sub.65 between instants t.sub.3 to t.sub.4 and t.sub.5 to t.sub.6 (see FIG. 1), all of which periods are relatively short, any reduction, even a small reduction, in the stabilization time would represent a considerable reduction in the cost of manufacturing such parts.
The aim of the Applicant is to reduce said stabilization time.
Thus, a first object of the present invention is to provide a device for leak testing at least a portion of the wall of a part by observing a filling pressure, with the stabilization time being reduced relative to that observed in comparable prior art methods, while still retaining their advantages of low cost, ease of implementation, etc. . .
A second object of the invention is to implement a method for relatively rapidly determining optimum parameters for defining leak test implementation using apparatus in accordance with the invention.